Electronic equipment racks are generally designed to receive a number of electronic components arranged vertically in the rack, mounted on shelves, and/or to front and rear mounting rails. The electronic equipment may include, for example, printed circuit boards, communications equipment, computers, including computer servers, or other electronic components.
Electronic equipment housed in racks produces a considerable amount of heat, which undesirably affects performance and reliability of the electronic equipment. Often the heat produced by the rack-mounted components is not evenly distributed in the racks. Inadequate supply of cool air and hot air recirculation can reduce equipment reliability substantially and can cause other performance problems. Accordingly, rack-mounted computer systems typically require effective cooling systems to maintain operational efficiency. Cooling can be accomplished by introducing cooled air into an equipment rack and causing the air to flow through equipment in the rack to remove some or all of the heat. The air exits the rack at an increased temperature.
A conventional solution for cooling racks of electronic equipment is to position the equipment racks in rows on a raised floor in a hot aisle and cold aisle configuration, with the fronts of the equipment racks in one row facing the fronts of the equipment racks in an adjacent row. Air cooled by a central air conditioning system is ducted under the raised floor, and perforated or vented floor tiles are provided in the cold aisles to release chilled air towards the fronts of the equipment racks. Chilled air is then drawn into the equipment mounted in the rack and heated air is exhausted out the back of each rack into the hot aisle.
The raised floor solution for cooling electronic equipment in data centers has several drawbacks. Raised floors are expensive, and may provide poor recirculation and delivery of air, particularly as the power density of equipment in racks is increasing. For example, releasing cooled air from a floor plenum is impractical, as there is a need for great volumes of cooled air to be pumped into the floor plenum before cooling can be effective. Even when great volumes of air are pumped into the floor plenums, chilled air exiting the perforated floor tiles may not reach the equipment mounted in the top portion of the equipment rack. Thus, equipment is often only loaded into lower portions of the racks, leaving a substantial area in the tops of the racks unused. Still further, it is not uncommon for warm air to travel back down into the floor plenums. Cutouts for equipment and cabling, gaps around tiles, and open tiles in the floor can lead to up to a 50% or greater loss of cooled air due to leakage, creating substantial inefficiency. Cabling and cooling lines are located below the floor, obstructing the path of the air as it moves toward the racks, which further creates inefficient cooling. Often, in data centers having raised floor solutions, the cooling units are located in the corners or on the edges of the rooms, causing racks in the center of the aisles or rooms to receive a substantially different volume of cool air than racks located near the perimeter of the room.
In addition, data rooms having raised floor cooling systems often require modifications, including modifications to allow for the addition or removal of equipment racks. Modifications can be problematic in a raised floor room. For example, a substantially large space is necessary to accommodate changes to the data center, as equipment being added or removed requires a ramp to move the equipment onto the raised floor. Also, in some data centers, the hot air is returned through the ceiling, requiring ceiling venting and ducts that may require substantial adjustment as other changes to the data center occur.
Further, the overall efficiency, cost, reliability and cooling capacity of a cooling system in a data center is directly related to the ability to prevent mixing of cooling air and warm exhaust air in the data center. Thus, effective cooling and air mixing separation methods are required.